The fabrication of integrated circuits (ICs) involves the formation of features on a substrate that make up circuit components, such as transistors, resistors, and capacitors. The devices are interconnected, enabling the IC to perform the desired functions. A transistor includes a gate and source/drain diffusion regions adjacent thereto. The gate includes a gate electrode over a gate dielectric. Conventional transistors use polysilicon as the gate electrode and silicon oxide as the gate dielectric. An IC typically comprises both p-type and n-type transistors, forming complementary metal oxide semiconductor (CMOS) ICs. To meet increasing performance needs, transistors with metal gates are becoming more prevalent. Metal gate transistors are fabricated using a replacement metal gate (RMG) process, sometimes referred to as a “gate last” process. It is therefore desirable to have improvements for fabrication of replacement metal gate transistors.